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Discussion Starter · #1 ·
Hi my name is Seth and I have recently purchased a 1985 Honda shadow VT 700. It has no spark I have replaced the battery, spark plugs, ignition coils, wires and boots, spark units, ignition switch, engine Killswitch, and check the resistance from the pulse generator plug in it is within spec. And I’m not that knowledgeable on motorcycle. Help needed. Thank you
 

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1983 Honda vt750 Shadow
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Did you ever have it running?
Each pulse generator set of wires measures 450 to 500 ohms?
On these older systems, you can put a 12 volt electrical test light on the negative connection of each coil, and it will blink as the control unit grounds the coil to fire the pug each revolution while cranking.
Ground the clip of the light and touch the tip to these wires.
See if you have battery power on the black/white wires first then see if the blue and the yellow will blink when cranking the engine.
You can find a good Honda manual here=

 

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'83 VT750C; ‘21 SV650A
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Wow. I’d almost accuse you of trolling us, because it sounds like you’ve replaced everything connected to a ‘no spark’ condition! 😳 Not bad for someone that claims not to know what they’re doing…

You turn the key and the lights come on. You press the start button and the engine turns over at a good speed. So everything should be getting power. At this point, the pulse generators usually test at 0 Ohms or the kill switch is usually off, dirty or disconnected for there to be no spark. Usually you get spark on ONE cylinder, at least! Aside from what @swifty2014 mentions, you could double check the wiring. Try disconnecting CDI Spark Unit #2 (should be above the starter motor) if you have it, just to check. There shouldn’t be any extra safety switches to mess with you on an ‘85. That being said, the electrics should indicate Neutral or the clutch being pulled in for the engine to be allowed to start.

A basic question, how are you checking for spark?
 

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Discussion Starter · #7 ·
Also @Troy Jollimore I do have a second problem that might help the first problem. When I push the start button it won’t crank. So I have been jumping the poles on the starter solenoid to crank it over. And I have replaced the solenoid
 

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Good to add, but if the wiring hasn’t been modified, that shouldn’t matter. The button cuts out the headlight and triggers that solenoid when pushed. If the system is getting power, it’ll just start with the solenoid shorted. That gets me thinking on the kill switch, though. You replaced the switch, but is it passing power through it at all? You should check the wiring, and clean/check the starter button at the same time.
 

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Discussion Starter · #10 ·
Hey guys thanks for all the help. And it work kinda. I have great spark on the rear cylinder. But the front cylinder’s spark is very weak. To the point that at some moments there is none. Any ideas. Thank you
 

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Check the connections at the coil terminals. Measure the spark plug wires for resistance. Shoulld be no more that 5000 ohms for each seperate wire since they have a resitor in the end caps.
Look for corrosion in the coil and end cap where the wires go in. They screw in.
 

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If that doesn’t work, you can try swapping the coils between cylinders, and then try swapping the two ignition boxes if the coils don’t show you anything. If the issue moves from one cylinder to the other, you’ve found the culprit.
 

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Discussion Starter · #17 ·
I am having a second problem with the carbs. Choke on it revs up to about 5000rpm. Choke off it idles like crap and when you give it some throttle it bogs down and dies
 

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Okay… on to the REAL fun and games! Old carburetors… almost as much fun as electrical. I would skip a lot of time and pain and just pull them out of the bike, especially if it’s been sitting for a while. Be careful not to hurt or tear the rubber boots that join them to the cylinder heads. Remove the bowls (bottom covers) off each one and send in a picture of how ghastly they look inside. Will probably need a GOOD cleaning. Or two…
 
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